NF-κB activation plays a role in superoxide-mediated cerebral endothelial dysfunction after hypoxia/reoxygenation

Background and Purpose - Cerebral vascular injury occurs in response to hypoxia/reoxygenation (H/R). However, the cellular signaling pathways that regulate this event remain unclear. The present study was designed to determine whether reactive oxygen species (ROS) mediate endothelial dysfunction after H/R in cerebral resistance arteries and, if so, the relative contribution of ROS, NADPH oxidase, and a nuclear factor-kappa B (NF-kappa B) pathway. Methods - Arterial diameter and intraluminal pressure were simultaneously measured on rat posterior cerebral arteries (PCA). Superoxide was measured by 5-mu mol/L lucigenin-enhanced chemiluminescence. Results - Hypoxia/reoxygenation selectively inhibited cerebral vasodilation to the endothelium-dependent agonist acetylcholine (Ach) (0.01 to 10 mu mol/L) by approximate to 50%. Impaired vasodilation after H/R was reversed by 2,2,6,6-tetramethylpiperidine-N-oxyl ( Tempo) ( 100 mu mol/L), a cell-permeable superoxide dismutase mimetic, and partially by ebselen ( 10 mu mol/L), a peroxynitrite scavenger. H/R-impaired vasodilation to Ach was also preserved by apocynin ( 1 mmol/L), a specific inhibitor for NADPH oxidase. Correspondingly, H/R significantly increased lucigenin-detectable superoxide, which was reduced by either Tempo or apocynin, but not by allopurinol ( 10 mu mol/L), an inhibitor of xanthine oxidase. Finally, the NF-kappa B inhibitors helenalin ( 10 mu mol/L) and MG-132 ( 1 mu mol/L) independently antagonized H/R-impaired Ach-induced vasodilation without affecting dilator response to sodium nitroprusside, an endothelium-independent vasodilator. Conclusions - These results indicate that superoxide mediates cerebral endothelial dysfunction after hypoxia/reoxygenation largely via activation of NADPH oxidase and possibly activation of NF-kappa B pathway.